1

Guidelines for Charging HFC-245fa to ORC Systems

This guideline provides general directions for charging HFC-245fa to ORC systems. 

This guideline is not meant to be a substitute for specific OEM instructions for leak 

checking, evacuation, or charging. It is always preferred that specific OEM instructions 

are followed when available. 

Positive-Pressure Leak Check 

Once the system is assembled it can be positive-pressure leak checked. It is important 

not to exceed any component pressure ratings when pressure testing. Consult the ORC 

equipment manufacturer to determine the acceptable pressure level that can be used for 

leak checking. The following information is general guidance. The system should be 

pressurized to 860kPa using dry nitrogen. An ultrasonic leak detector is then used to 

detect leaks. Alternatively, a refrigerant such as R-134a can be used as a trace gas when 

an electronic refrigerant leak detector is used. This can be accomplished by adding R134a refrigerant to a pressure of 69kPa and then adding dry nitrogen until the pressure is 

860kPa. A leak detector capable of detecting HFC refrigerants would then be used to 

locate any leaks. After leak check, the refrigerant/nitrogen mixture would be recovered. 

Then the system would need to be evacuated to remove any remaining non-condensables 

and moisture. 

 

Evacuation/Vacuum Leak Check 

Evacuate system to less than 1,000 microns (mercury) pressure. Use a good vacuum 

gauge, such as an electronic vacuum gauge to measure pressure. Place the gauge at the 

opposite end of the vacuum train as far as possible from the vacuum pump. 

(See Figure 1.) After evacuation, isolate the vacuum pump from the system and monitor 

the system pressure for 10 minutes. If vacuum pressure should not rise more than 300 

microns in 10 minutes, the system is tight. If vacuum pressure rises more than 300 

microns and then becomes steady, there is still moisture in the system. Additional 

evacuation is required. If pressure rises continuously, there is a leak in the system. 

For small systems, it may not be necessary to break vacuum using HFC-245fa vapor. To 

minimize the likelihood of heat exchanger tube icing in large systems, break vacuum by 

first charging HFC-245fa vapor until system pressure is above 11.0 inches of mercury 

vacuum. (See Figure 3.) Be sure to maintain cooling water flow or fans (air-cooled 

systems) during charging. A charging line is connected between the vapor access port of 

the source cylinder to an appropriate vapor connection on the system.
2

Charging HFC-245fa 

Gravity Charging From Single Port Cylinders

Connect the HFC-245fa cylinder to the system as shown in Figure 2. Elevate the cylinder 

so that it is above the height of the liquid reservoir receiving the charge. If the cylinder 

temperature is cooler than the system temperature, it may be necessary to warm the 

cylinder. A commercially available cylinder heating apparatus with appropriate 

temperature controls such as cylinder heating blanket may be used. Alternatively, warm 

water (125F or less) can be used to heat the cylinder. 

Pump-Assisted Charging From Single Port Cylinders. 

A gear pump can be used to transfer liquid HFC-245fa. Graphite or stainless steel gears 

are acceptable. Polymeric gears such as PTFE may swell enough to bind the gears and 

are thus not recommended. 

Caution: Do not operate the transfer pump with the downstream service valve closed. 

“Dead heading” the pump can lead to component damage or failure. Serious injury can 

occur depending on the mode of failure. 

When using a pump to assist with liquid transfer, a transfer line is connected between the 

HFC-245fa source cylinder liquid port and the pump suction. A transfer line is connected 

between the pump discharge and the liquid side of the system. If possible, position the 

pump lower than the HFC-245fa source cylinder so adequate pump suction head is 

maintained. If the HFC-245fa source cylinder can not be elevated above the height of 

the liquid reservoir receiving the charge, it may become necessary to warm the cylinder 

in order to create an adequate pressure differential. The previous section discusses 

cylinder heating methods. Additionally, if pump cavitation occurs, the transfer line 

between the pump and source cylinder can be formed into a coil and immersed in water 

ice or dry ice to prevent pump cavitation. (See Figure 2.) 

Charging from Containers having Separate Liquid and Vapor Ports

When the refrigerant source container is equipped with both liquid and vapor ports, the 

push-pull liquid transfer method can be used. (See Figure 3.) A vapor line is connected 

between the vapor port of the HFC-245fa source container and the vapor side of the 

system. A section of liquid transfer line is connected between the HFC-245fa source 

container liquid port and the pump suction. A section of liquid transfer line is connected 

between the pump discharge and the liquid side of the system. 
3

Other Equipment 

A refrigerant recovery unit may be used in place of a liquid transfer pump. Consult the 

recovery equipment manufacturer for the recommended connections and procedures. A 

refrigerant recovery unit provides a convenient means to recover liquid from the liquid 

transfer line after charging been completed. 

 

ORCS

Vapor Service Port

Vacuum Pump*

Figure 1 -System Evacuation

Vacuum gauge 

(locate away from vacuum pump)

*

If a recovery/charging unit is used instead of a vacuum pump, consult the recovery equipment manufacturer for 

recommended evacuation connections and procedure. 

Vent to a safe outside location

ORCS

Vapor Service Port

Vacuum Pump*

Figure 1 -System Evacuation

Vacuum gauge 

(locate away from vacuum pump)

*

If a recovery/charging unit is used instead of a vacuum pump, consult the recovery equipment manufacturer for 

recommended evacuation connections and procedure. 

Vent to a safe outside location

ORCS

Vapor Service Port

Liquid Service Port

Pump (Optional)

Wet or Dry Ice

(Optional)

Cylinder 

Liquid Port

Figure 2 - Single Port Cylinder : Gravity or Pump-Assisted Charging

Warming of cylinder

may be required –

a commercially available

cylinder heating blanket 

is recommended.

Cylinders that do not have a dip tube 

Need to be inverted to deliver liquid.

Vacuum Gauge

Evacuated system

ORCS

Vapor Service Port

Liquid Service Port

Pump (Optional)

Wet or Dry Ice

(Optional)

Cylinder 

Liquid Port

Figure 2 - Single Port Cylinder : Gravity or Pump-Assisted Charging

Warming of cylinder

may be required –

a commercially available

cylinder heating blanket 

is recommended.

Cylinders that do not have a dip tube 

Need to be inverted to deliver liquid.

Vacuum Gauge

Evacuated system
4

Disclaimer 

Although all statements and information contained herein are believed to be accurate and reliable, they are 

presented without guarantee or warranty of any kind, expressed or implied. Information provided herein

does not relieve the user from the responsibility of carrying out its own tests and experiments, and the user 

assumes all risks and liability for use of the information and results obtained. Statements or suggestions 

concerning the use of materials and processes are made without representation or warranty that any such 

use is free of patent infringement and are not recommendations to infringe on any patents. The user should 

not assume that all toxicity data and safety measures are indicated herein or that other measures may not be 

required. 

ORCS

Vapor Service Port

Liquid Service Port

Pump*

Wet or Dry Ice

(Optional)

Figure 3 - Dual Port Cylinder: Push/Pull Charging

Liquid Port Vapor Port

HFC-245fa cylinder

*

If a recovery/charging unit is used instead of a pump, consult the recovery equipment manufacturer for recommended

connections and charging/recovery procedures. 

1) For large systems, break vacuum by first charging vapor to a system pressure of 11.0 inches of mercury vacuum.

2) Open cylinder liquid port and valves along liquid transfer line, then start pump to begin charging liquid. 

Vacuum Gauge

ORCS

Vapor Service Port

Liquid Service Port

Pump*

Wet or Dry Ice

(Optional)

Figure 3 - Dual Port Cylinder: Push/Pull Charging

Liquid Port Vapor Port

HFC-245fa cylinder

*

If a recovery/charging unit is used instead of a pump, consult the recovery equipment manufacturer for recommended

connections and charging/recovery procedures. 

1) For large systems, break vacuum by first charging vapor to a system pressure of 11.0 inches of mercury vacuum.

2) Open cylinder liquid port and valves along liquid transfer line, then start pump to begin charging liquid. 

Vacuum Gauge